When you are a missionary you have rules that you are supposed to live by, one of them is no tv, or listening to music with earphones, so when you are on a plane for a long period of time you have the choice to sleep, eat, talk, or read. So I always make sure to send some reading material. Of course it is missionary approved. Yes, there are also guidelines on what missionaries can read. I think the General Conference Ensign is a must. Oh, and letters from home. You know the ones where you pour your heart out or give them all that advice, the advice that you have been trying to tell them and you know they are only half listening, but now they are fresh out of the MTC and they hear you differently. All that stuff you tried to tell them, well they actually care a little bit more and even want to hear it. A few other things that can come in handy are travel size medications as well as some of their favorite snacks. I know for my daughter it was her first time on an airplane and so I loaded her up with any and every medication I could possibly think she might need.
I obviously took two different approaches to these packages. I found myself singing the song "I'm Leaving On A Jet Plane" by Peter Paul & Mary when I put together my daughter's package and with my son it was "Russia or Bust!" The thing I love about this is that it can be whatever you want it to be. But I do understand that sometimes it is nice to see that someone already came up with a direction for you to go.
On this package for my daughter I found an image of a jet plane and just traced it on white paper and then cut it out (I am one of those weird people who still cuts things out by hand because I like it) and then start writing.
